Fine grinding apparatus

ABSTRACT

An apparatus for fine grinding using spherical agitating elements maintained in kinetically activated condition within a liquid by agitating means comprising arms or the like attached to a central vertical shaft, discs are provided around the shaft at intervals to prevent liquid containing the agitating elements from rising adjacent the shaft.

United States Patent 72] Inventor Andrew Szegvari 201 Castle Blvtl, Akron, Ohio 44313 2: Appl, No. 745,150

[22] Filed July 16,1968 [45] Patented Aug. 24, 1971 [32] Priority July 17, 1967 [33] Great Britain [3 1 32770167 [54] FINE GRINDING APPARATUS 17 Claims, 5 Drawing 1'15.

[52] US. Cl 241/46, 241/172,259/107 [51] lnt.Cl B02c 17/16 [50] Field ofSeareh 241/46,

[56] References Cited UNITED STATES PATENTS 677,702 7/1901 Russell 241/188 X 3,432,109 3/1969 Geissel 241/172 3,458,144 7/1969 Lessells 241/4602 Primary ExaminerDonald G. Kelly Attorney-Gordon C. Mack ABSTRACT: An apparatus for fine grinding using spherical agitating elements maintained in kinetically activated condition within a liquid by agitating means comprising arms or the like attached to a central vertical shaft, discs are provided around the shaft at intervals to prevent liquid containing the agitating elements from rising adjacent the shaft.

PATENTEU Auc24|sn 3,601,322

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PAIENTEU 4119241911 3.601.322

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INVENTOR. ANDREW SZEGVARI ATTORNE Y FINE GRINDING APPARATUS r The present invention relates to an improved apparatus for grinding and dispersing solid particlescontained'ina liquid medium by means of amass of balls or otherdiscrete elements agitated by means of a rotating agitator within the liquid medium, and to an improved agitator for such apparatus.

The invention is particularly concerned with that type of apparatus in which the grinding elements are agitated by an agitator having agitating members which move through the mass of elements to keep the elements in random relative motion so that they exert attritive action on material prese'nt in said mass of agitated media, as is described in U.S. Pat. No.- 2,784,359 or with a continuous process such asfor example, is described and claimed in U.S. Pat. No. 3,149,789.

The grinding apparatus of this invention is sharply distinguished from apparatus where grinding media such as Ottawa sand is thrown outwards against the wall of the grinding vessel by discs on a rotating shaft. n the contrary in the apparatus of this invention the agitator members maintain the grinding elements in kinetically activated condition within the liquid rather than in group' movement and to concentrate the maximum activity away from the wall of the vessel.

However, there is a tendency for the activating action along and in thevicinity around the shaft to be less effective than at regions of the chamber spaced from the shaft in which agitation is taking placev 1 v Such nonuniform action is believed to be attributable to a number ofcauses, viz, the material has a shorter path through the chamber in the immediate vicinity of the shaft; the effective speed of rotation of the agitator members is lower nearer the shaft than at regions further from the shaft; and. in cases where the chamber is externally cooled the less effectively cooledliquid material in the immediate vicinity of the shaft may be more fluid than the material in the outer regions of the chamberand thus flow more readily through the chamberthan the more effectively cooled material.

around the shaft, and the agitator members and/or the bafiling means may be constructed to obviate or lessen this tendency.

This may be effected in numerous'ways, e.g., by vanes or ribs or other means'constructed and arranged to have an outward force on the material when it has flowed or been induced towards the shaft.

The discs may alternatively be freely mounted about the shaft. The agitator members and the discs may be perpendicular to the shaft or arranged inplanes at a suitable oblique inclination thereto. The discs could'be'arranged'to wobble with reference to the shaft.

An alternative form of baffling means comprises spiral webs or plates attached to or loosely mounted about the shaft.

A mass of small spherical or substantially spherical elements .is preferred since in the process of the invention elements of any other shape or of irregular shape are likely to jam and interfere with that random distribution of the momentum of the elements which is aimed at. Balls of a diameter between one sixty-fourth inch and nine-sixteenths inch are found very suitable. Balls of steel or of a'ceramic material having a specific gravity of 2 or more are advantageous, e.g., they may be of a ceramic material such as steatite', aluminum oxide, zirconia or To the foregoing ends, the invention proposes to provide between agitator members, means .for baffling or preventing undesired flow of the liquid material along and immediately around the shaft. Thus the distribution curve based onparticle size and size frequency may bemaderelatively narrow in the direction of particle size. The agitator members may be of varied description, e.g., they may be arms extending through the shaft 'or fixed tangentially to .the shaft, and arranged in different angular relationships as seen from the end of the shaft (e.g., with alternate arms .at right angles to the remaining arms) preferably with each arm projecting to a greater extent from the shaft at one end than at the other; they may be eccentrically arranged rings secured to the shaft at respectively different angular positions around the shaft as in U.S. Pat. No. 3,243,128, or of any other form which would permit the flow of the liquid material along and immediately around the shaft in the absence of the baffling means' provided by the present. invention.

The baffle members may take the form of discs attached to or integral with the shaft between agitator members, e;g., as is hereinafter more particularly described. There may be a disc 7 to each pair of agitator members.

made integral therewith. However, for structural strength the discs may. be provided with bosses so that in the axial direction they occupy the distance between adjacent agitator members.

' Further members may be provided for directing the liquid outwards or inwards in relation to the shaft between the agitator members. v The. presence of the baffling means may in some cases give rise to a tendency for-a dead space or spaces to be produced projection from the shaft of hafnium'dioxide. Small rounded pebbles will also serve. The speed of rotation of the agitator depends inter alia on the size of the balls.

' I have further found thataccording to the specific gravity of the grinding media, the apparatus may be designed to produce a lifting or depressing action on the media, or alternatively a lift action may be produced in one region, such as the lower region of the chamber and a depressing action at another re-' gion, e.g., the upper region of the chamber.

The tendency is for the agitator members to direct the liquid material in a helical path through the vessel and by choosing the direction of rotation lift or depressing action can be layers with larger media at the bottom or inlet end and smaller media at the other end, or layers may be graduated as to the size of the media and provision made for separating the layers.

In order that the invention may be the more clearly understood, reference is hereinafter made to the accompanying drawings which illustrate one embodiment thereof.

FIG. 1 is a sectional elevation of a continuous grinding and dispersing vessel; r a

-' FIG. 2 is a cross-sectional plan view of the agitator through one of the agitator members;

FIG. 3 is an enlarged fragmentary view showing two agitator members and their element-activating action and one baffle disc interposed between them;

FIG. 4 is a section through a vessel equipped with a baffle and eccentrically positioned rings to serve as agitating members; and i FIG. 5 is a section on line 5-5 of FIG. 4.

The continuous means shown comprises a deep cylindrical vessel '1. The inlet 2 will receive the liquid material to be treated, e.g., supplied by a pump, and the material usually flows past a sieve in the top of the vessel through a suitable outlet which may be arranged at the top of the vessel or substantially so, the sieve permitting flow of the treated liquid but holding back the grinding elements, as is known.

The vessel is charged with a mass of spherical-grinding elements 3. I v

An agitator 4 is provided in the vessel and comprises a shaft '5 extending axially of the vessel to near the inlet end thereof.

The agitator comprises multiple agitator members in the form of radial arms 6, in this-instance of circular section, alternating arms 6a being disposed at right angles to the remainder 6b when viewed from the end of the shaft. Each arm extends further at one side of the shaft than the other and those in each group are in staggered relationship, i.e., alternate arms 6a extend more at one side of the shaft and the remaining arms 6a extend further at the other side of the shaft. The same applies to the arms 6b. The arms in the form illustrated in FIGS. 1 and 2 are arranged tangentially of the shaft alternating in each group from one side to the other of the shaft.

in this case each arm may be located in a chordal groove in the shaft and cross-bolted to the shaft by a net 7 and bolt 8. The bolthead may be countersunk as shown.

Between the arms of each pair is disposed a disc 9 attached to a boss 10 attached to the shaft and forming a baffle member.

The disc and boss unit is of a depth corresponding to the spacing between the arms of the pair for facilitating structural strength of the agitator.

The action of the agitator members and the discs will be clear from FIG. 3. During rotation of the shaft the arms move progressively through the mass of balls and they activate the balls to keep them in a state of relative motion with an especially intense activating action at the outer free ends as indicated by the arrows A. Distribution of this activation is facilitated by the fact that the ends of the arms travel in different circular paths.

The action of the discs is to baffle the flow of the liquid medium immediately around and along the shaft. As depicted by the arrows B they deflect the liquid medium outwards, but they are of a diameter less than the length of the arms, so that they do not interfere with the activating action of each end of each arm.

The arms in FIG. 3 are formed by rods or bars passing through apertures in the shaft.

The speed at which the shaft is rotated depends inter alia upon the size of the spherical elements. With elements of a diameter of one-eighth inch upwards, a suitable speed is 100-150 r.p.m., with elements of a diameter of three thirtyseconds to one-eighth inch a suitable speed is from 300 to 600 rpm. and with elements below three thirty-seconds inch a suitable speed is 400800 r.p.m.

F168. 4 and 5 illustrate a vessel with a vertical agitator shaft 14 to which the baffle l5 and eccentric rings l8, l9 and are attached, the latter to serve as agitating members.

I claim:

1. An agitator for a cylindrical vessel comprising agitating members arranged along and projecting outwardly from a shaft and comprising baffle means for baffling flow of liquid material along and immediately around the shaft, portions of agitating members which extend the greatest distance from the shaft extending a greater distance from the shaft than the portion of the baffle means farthest from the shaft.

2. An agitator according to claim 1, in which the baffle means are in the form of discs and at least one portion of each agitating member projects outwardly beyond the periphery of the discs.

3. An agitator according to claim 1 in which the baffle means are fixed in relation to the shaft.

4. An agitator according to claim 1 in which the baffle means are freely mounted in relation to the shaft.

5. An agitator according to claim 2 in which the discs have bosses so that in the axial direction they occupy the distance between adjacent agitator members.

6. An agitator according to claim 1 in which the agitating members are in the form of arms and adjacent arms extend from the shaft at an angle to one another.

7. An agitator according to claim 1 in which the agitator members are in the form of arms and they are attached substantially tangentially to the shaft.

8. An agitator member according to claim 1, in which the agitator members are in the form of eccentrically disposed rings with adjacent rings extending in different directions from the shaft.

9. Agitating equipment which comprises a vessel adapted to retain a liquid, and an inlet opening at the bottom of the vessel, the vessel containing a mass of grinding elements and a vertical shaft with agitating members arranged along the shaft and projecting from the shaft with the portions thereof farthest from the shaft spaced from the inner surface of the vessel, and means arranged along the shaft and projecting from it a lesser distance than the agitating members to baffle the flow of liquid along and immediately around the shaft when the shaft is rotated while the vessel contains liquid.

10. The equipment of claim 9 in which the agitating members are arms and the ends of each arm extend different distances from the shaft.

11. The equipment of claim 10 in which each arm is substantially tangential to the shaft.

12. The equipment of claim 10 in which adjacent arms extend from the shaft at an angle to one another.

13. The equipment of claim 9 in which each baffle means is a disc.

14. The equipment of claim 13 in which at least a portion of each agitating member projects outwardly beyond the periphery ofthe discs.

15. The equipment of claim 13 in which the disc is attached to the shaft so as to be freely rotatable about it.

16. The equipment of claim 13 in which each disc is attached to the shaft by a boss, the disc and boss are situated immediately between two arms, and said two arms are at to one another.

17. The equipment of claim 9 in which the agitating members are in the form of eccentrically disposed rings with adjacent rings extending in different directions from the shaft.

PO- m v Patent No. 3,661,322

Inventcr(s} Andrew Szegvasri 

1. An agitator for a cylindrical vessel comprising agitating members arranged along and projecting outwardly from a shaft and comprising baffle means for baffling flow of liquid material along and immediately around the shaft, portions of agitating members which extend the greatest distance from the shaft extending a greater distance from the shaft than the portion of the baffle means farthest from the shaft.
 2. An agitator according to claim 1, in which the baffle means are in the form of discs and at least one portion of each agitating member projects outwardly beyond the periphery of the Discs.
 3. An agitator according to claim 1 in which the baffle means are fixed in relation to the shaft.
 4. An agitator according to claim 1 in which the baffle means are freely mounted in relation to the shaft.
 5. An agitator according to claim 2 in which the discs have bosses so that in the axial direction they occupy the distance between adjacent agitator members.
 6. An agitator according to claim 1 in which the agitating members are in the form of arms and adjacent arms extend from the shaft at an angle to one another.
 7. An agitator according to claim 1 in which the agitator members are in the form of arms and they are attached substantially tangentially to the shaft.
 8. An agitator member according to claim 1, in which the agitator members are in the form of eccentrically disposed rings with adjacent rings extending in different directions from the shaft.
 9. Agitating equipment which comprises a vessel adapted to retain a liquid, and an inlet opening at the bottom of the vessel, the vessel containing a mass of grinding elements and a vertical shaft with agitating members arranged along the shaft and projecting from the shaft with the portions thereof farthest from the shaft spaced from the inner surface of the vessel, and means arranged along the shaft and projecting from it a lesser distance than the agitating members to baffle the flow of liquid along and immediately around the shaft when the shaft is rotated while the vessel contains liquid.
 10. The equipment of claim 9 in which the agitating members are arms and the ends of each arm extend different distances from the shaft.
 11. The equipment of claim 10 in which each arm is substantially tangential to the shaft.
 12. The equipment of claim 10 in which adjacent arms extend from the shaft at an angle to one another.
 13. The equipment of claim 9 in which each baffle means is a disc.
 14. The equipment of claim 13 in which at least a portion of each agitating member projects outwardly beyond the periphery of the discs.
 15. The equipment of claim 13 in which the disc is attached to the shaft so as to be freely rotatable about it.
 16. The equipment of claim 13 in which each disc is attached to the shaft by a boss, the disc and boss are situated immediately between two arms, and said two arms are at 90* to one another.
 17. The equipment of claim 9 in which the agitating members are in the form of eccentrically disposed rings with adjacent rings extending in different directions from the shaft. 